Tax Break Costs

By National Priorities Project

Introduction

Since 1974, the federal government has published estimates of revenue lost due to tax credits, deductions, and loopholes. National Priorities Project compiled these historic estimates into a single file and normalized the names and categories over time.

Using that file as an input, we created another, more useful version of the data by:

• inflation adjusting the dollar amounts
• expressing amounts as a % of gross domestic product (GDP)
• calculating % change over the previous year
• expressing each tax break cost as a percent of the year's total

This project contains the input files and code used to create the final version of the tax break cost time series posted on our website.

Usage

Make sure the dependencies are installed and then run the script to build the complete tax break file:

python build_tax_breaks.py

Note: To use a different base year when adjusting for inflation, change PRICE_INDEX_BASE_YEAR at the top of the script.

Output

The script will write out two files:

1. tax-break-complete.csv: Input records are unchanged but now have additional information (inflation-adjusted dollars, percent change, etc.)
2. tax-break-complete-combined-for-cbo: Some individual tax breaks have been combined to mirror tax break estimates used by the Congressional Budget Office when calculating distributional effects (as documented here).

Documentation and Methodology

Complete documentation about the data sources and the methodology for creating the input file can be found at http://nationalpriorities.org/en/analysis/2013/big-money-tax-breaks/tax-breaks-notes-and-sources/